LIGHTING MODULE FOR MOTOR VEHICLES AND LIGHTING AND / OR SIGNAL DEVICE EQUIPPED WITH SUCH A MODULE

Description

[0001] The present invention relates in particular to a light module for a motor vehicle, and to a lighting and / or signaling device equipped with such a module.

[0002] A preferred application is in the automotive industry, for vehicle equipment, particularly for the creation of devices capable of emitting light beams, also known as lighting and / or signaling functions, generally compliant with regulations. For example, the invention can enable the production of a light beam, preferably highly resolved, of a pixelated type, notably for signaling and / or contributing to lighting functions at the front of a vehicle. It can be used to display pictograms or variable patterns on a projection surface of the outgoing light.

[0003] Vehicle signaling and / or lighting devices are luminous systems comprising one or more light sources and a lens that closes the light. In simplified terms, the light source emits light rays to form a beam that is directed towards the lens to produce an illuminated area that transmits light outside the vehicle. These functions must comply with regulations regarding luminous intensity and visibility angles, among other things. Current lighting and signaling modules are designed to emit, for example: a dipped beam, directed downwards, sometimes still called a dipped beam and used when other vehicles are present on the roadway; a main beam without a cutoff, and characterized by maximum illumination in the axis of the vehicle; a fog light beam, characterized by a flat cutoff and a large illumination width; a signal beam for traffic in town, also called a city lamp.

[0004] Recently, technologies have been developed to produce high-definition pixelated or segmented beams, with a resolution of at least 1000 segments, notably through micro or nano electromechanical devices called MEMS or NEMS, respectively. Due to the great flexibility in beam shape and pattern they offer, and because their cost is decreasing, these systems are increasingly being implemented in more and more critical applications, particularly in headlights at the front of vehicles. figure 1 This gives an example of the implementation of a pixelated and digital imaging system in the form of a micromirror array 13 within a beam projection module. A light source 11 generates light rays towards an optical device 12, which generates a beam that impacts a reflective face 14 of a micromirror array 13. Depending on the controlled inclination of the mirrors, the light is either reflected back towards the projection device 15 or reflected into a dead zone so as not to contribute to active illumination.

[0005] In some cases, this requires significant output illumination, particularly sufficient to meet regulatory luminous flux requirements. However, achieving significant illumination is difficult given the layout illustrated in the... figure 1 It is easy to understand that increasing the magnification of the lens used for the input device 12 or bringing it closer to the micromirror array 13 quickly poses an interference problem with the lens used as the projection device 15. In the example shown, the beam envelope delimited by rays a1, a2 is on the verge of interfering with the edge of the projection device 15; similarly, the rays b1, b2 reflected by the array 13 are transmitted by the device 15 as rays c1, c2, on the verge of interfering with the input device 12. Taking this limitation into account, patent document WO 2017 / 143371 A1 discloses a projector for a motor vehicle comprising a micromirror array and equipped with a pair of LED light sources, each associated with a focusing lens for a light beam onto the reflective surface of the micromirror array.This doubling of light sources obviously increases the luminous flux emitted by the projector. However, it inevitably increases the cost and size.

[0006] Document GB 2418996 A describes a light module according to the preamble of claim 1.

[0007] The present invention aims to remedy, at least in part, the drawbacks of current techniques.

[0008] The present invention relates, according to one aspect, to a light module for a motor vehicle configured to produce an output beam, comprising a light source including at least one light-emitting diode, a pixelated digital imaging system, and an interposed optical input device, following the path of the light rays from the light source between the light source and the pixelated digital imaging system so as to transmit at least a part, called the transmitted part, of the light rays from the light source to an impact surface of the pixelated digital imaging system.

[0009] According to the invention, it comprises a prism, including a first face, a second face and a third face, and configured for: transmit between the first face and the third face at least a part of the light rays from the transmitted part to the impact surface; form reflected rays by reflection of at least a part of the light rays returned by the impact surface, by total internal reflection on the first face; return at least a part of the reflected rays to a projection area via the second face.

[0010] In addition, a pane of glass is arranged between the impact surface and the third face, and a solid interface joins the third face and a face of the glass arranged opposite the third face.

[0011] According to the invention, the interface material, the glass material, and the prism material have the same refractive index, or refractive indices that do not differ from each other by more than 10%. Under these conditions, stray reflections due to Fresnel's laws are eliminated or greatly reduced, which is all the more beneficial to the module's efficiency.

[0012] Thus, the light rays are deflected during their path from the light source to the projection device, at least partially by the prism. The prism's function includes, upstream of the imaging system, the transmission of light rays from the source and, downstream of the imaging system, total internal reflection, allowing for a significant angular change in the rays, advantageously directing the rays exiting the prism towards the projection device. The prism permits large angular variations in the beam direction between the beam upstream of the imaging system and the beam downstream of it.

[0013] This allows for easy adjustment of the position and angle of the optical device located at the input, without being hindered by space constraints relative to the optical projection device, unlike the prior art illustrated in the figure 1 The optical input device can be advantageously moved closer to the imaging system and / or its diameter increased (the increase in illumination is directly related to the increase in the diameter of a lens). By doing so, the luminous efficacy of the beam impacting the imaging system is higher, which makes it possible, despite the use of a light-emitting diode source, to obtain satisfactory output illumination.

[0014] Furthermore, the assembly of the glass onto the third face of the prism via a solid interface, such as adhesive, ensures continuous transmission of light rays between these two parts. This prevents potential reflection phenomena at a solid / air / solid interface; however, such unwanted reflections could lead to the re-emission of stray light rays and their projection onto the road along with the desired effective beam, thus limiting the potential applications of pixelated beams, particularly in the automotive sector, especially for anti-glare road beam applications.While the imaging device and optical elements are currently considered complementary but separate components of a light module, the present invention challenges this misconception and integrates them more closely by combining a glass panel of the imaging device and a prism face without any interstitial air gap. The presence of this interface also facilitates adjustment of refractive index variations along the path of the light rays, whereas the air gap is currently automatically encountered. Depending on a preferred aspect, similar or identical refractive indices are selected, as will be explained later.

[0015] In another aspect, the present invention also relates to a motor vehicle lighting and / or signaling device equipped with at least one light module. This device may include at least one additional module comprising at least one of the following: an additional module configured to produce a basic low beam and an additional module configured to produce a basic high beam.

[0016] Advantageously, the pixelated beam can be an effective complement to another beam, or even several. In particular, in a preferred case, the device includes an additional module configured to produce a basic low beam and an additional module configured to produce a basic high beam, and in which the output beam of the module partially overlaps both the basic high beam and / or the basic low beam.

[0017] The present invention also relates to a vehicle equipped with at least one module and / or device according to the present invention.

[0018] Preferably, the interface is a polymerized optical adhesive.

[0019] In some cases, the maximum thickness of the adhesive interface is less than 1 mm, or even 0.5 mm.

[0020] In a preferred case, the third face and the glass face are parallel. Thus, the interface thickness is constant.

[0021] According to a particularly advantageous embodiment, the module is such that the second face and the third face are supported by two planes perpendicular to each other.

[0022] In addition, it preferably includes an optical device for projecting the output beam, receiving at least part of the reflected rays.

[0023] Advantageously, the optical projection device has an optical axis perpendicular to the second face.

[0024] Optionally, the projection optical device features an optical axis forming an obtuse angle with the average direction of the transmitted portion. This feature is very useful for reducing size and allows for greater flexibility in lens size for the input optical device.

[0025] In a non-limiting case, the third face is parallel to the impact surface. Advantageously and preferably, the third face has an anti-reflective coating. This avoids ghosting phenomena that can be produced by strong reflections back from the mirrors onto the third face.

[0026] In one embodiment, the prism is made of a material whose Abbe number is greater than or equal to 50.

[0027] According to the invention, the prism is made of PMMA or Crown glass.

[0028] According to the invention, a pane of glass is arranged between the impact surface and the third face.

[0029] According to the invention, a first face of the glass is located opposite the impact surface and includes an anti-reflective coating. This prevents the ghosting phenomenon that can be produced by strong reflections back from the mirrors onto the glass.

[0030] Advantageously, the anti-reflective coating is configured to reflect less than 4%, preferably less than 2% of the light rays in the visible range.

[0031] Preferably, the average direction of the transmitted part forms, with a normal to the first face, an angle between -20° and +20°.

[0032] Preferably, the distance separating the impact surface and the third face is less than or equal to 2 mm, and preferably less than or equal to 1 mm.

[0033] In one embodiment, the pixelated digital imaging system includes a micro-mirror array.

[0034] Optionally, the output beam is configured to project at least one pictogram pattern.

[0035] In a preferred embodiment, the module is configured to project a beam of light at the front of a motor vehicle.

[0036] Other features and advantages of the present invention will be better understood with the aid of the exemplary description and drawings, among which: there figure 1 shows a schematic representation of a pixelated beam projection according to the prior art; the figure 2 represents an example of the realization of the invention.

[0037] Unless specifically stated otherwise, technical features described in detail for a given embodiment may be combined with technical features described in the context of other embodiments described by way of example and not limitation.

[0038] In the characteristics described below, the terms verticality, horizontality, and transverseity, or their equivalents, refer to the position in which the lighting module is intended to be mounted in a vehicle. The terms "vertical" and "horizontal" are used in this description to designate directions, with "vertical" being perpendicular to the horizontal plane and "horizontal" parallel to the horizontal plane. These directions are to be considered under the operating conditions of the device in a vehicle. The use of these terms does not imply that slight variations around the vertical and horizontal directions are excluded from the invention. For example, an inclination of + or - 10° relative to these directions is considered a minor variation around the two preferred directions.

[0039] The device of the invention incorporates at least one module for generating a pixelated beam, but preferably also projects at least one other beam via at least one other module. The device of the invention can therefore be complex and combine several modules, which may also share components.

[0040] In the context of this invention, a dipped beam is defined as a beam used when vehicles are being overtaken and / or followed, and / or other elements (people, obstacles, etc.) are present on or near the roadway. This beam has a downward average direction. It may optionally be characterized by the absence of light above a plane inclined at 1% downwards on the side of the road where traffic is traveling in the opposite direction, and above another plane inclined at 15 degrees to the first on the side of the road where traffic is traveling in the same direction. These two planes define a cutoff conforming to European regulations. This upper downward cutoff is designed to prevent dazzling other road users in the roadway extending in front of the vehicle or on the roadside.The dipped beam, formerly from a simple projector, has undergone evolutions, the dipped beam function being able to be coupled with other lighting characteristics which are still considered as dipped beam functions within the meaning of the present invention.

[0041] This includes, in particular, the following functions: The AFS beam (short for "Advanced Frontlighting System") offers several other beam types. These include the BL (Bending Light) function, which can be broken down into DBL (Dynamic Bending Light) and FBL (Fixed Bending Light); the Town Light beam, for city lighting. This function widens a low beam while slightly reducing its range; and the Motorway Light beam, for highway lighting, provides the highway function. This function increases the range of a low beam by concentrating the light beam at the optical axis of the headlight unit. Overhead Light (OWL) is a beam used for overhead gantries. This function modifies a typical low beam so that overhead gantries are adequately illuminated by the low beams; it is also known as Adverse Weather Light (AWL).

[0042] The basic high beam's function is to illuminate a wide area in front of the vehicle, as well as a considerable distance, typically around 200 meters. This beam, by its very nature, is primarily positioned above the horizon line. It may, for example, have a slightly upward optical axis of illumination.

[0043] The device can also be used to create other lighting functions via or outside of those described previously.

[0044] As previously mentioned, one aspect of the invention relates to a module for generating a pixelated output beam, that is, a beam processed by a digital pixelated imaging system offering high flexibility, through control of the imaging system, in terms of the configurations of the beams actually projected. The terms "digital pixelated imaging system," "pixelated beam imaging system," or their equivalents are defined as a system emitting a light beam, said light beam being composed of a plurality of light sub-beams, each light sub-beam being controllable independently of the other light sub-beams. These systems can be, for example, micromirror arrays 23 as shown, liquid crystal devices, or digital light processing (DLP) technology.Micromirror matrices are also called, in Anglo-Saxon terms, "Digital Micromirror Device" (DMD).

[0045] Each independently controllable sub-beam forms a pixelated beam. The micromirror arrays are controlled by electronic control units. Each micromirror preferentially has two operating positions. An active position corresponds to an orientation of the micromirrors that allows reflection of an incident light beam towards an output surface. A passive position corresponds to an orientation of the micromirrors that allows reflection of an incident light beam towards an absorbing surface, i.e., towards a direction different from that of the output surface. Generally, this type of imaging system is implemented in mechanical microelectronic systems known as MEMS, which, in this application, also includes nanosystems known as NEMS.

[0046] In a manner known per se, a light source 21 is used to illuminate an impact surface 24 of the pixelated imaging system, for example, the reflective face of the micromirrors in a micromirror array 23, and the rays processed by the pixelated imaging system are reflected back for projection, generally via an optical output element such as a projector screen or a projection lens. Generally, the present invention can use light sources of the type light-emitting diodes, commonly known as LEDs. These may optionally be organic LED(s). In particular, these LEDs may be equipped with at least one chip capable of emitting light of adjustable intensity, depending on the lighting and / or signaling function to be performed.Furthermore, the term "light source" here refers to an assembly of at least one elementary source, such as an LED, capable of producing a flux that generates at least one light beam at the output of the module of the invention. In an advantageous configuration, the output face of the source has a rectangular cross-section, which is typical for LED chips. By way of example, the light source 21 is configured to produce a luminous flux greater than 3000 lm, and for example, on the order of 4000 lm.

[0047] The potential of pixelated beams in the automotive field and the increased functionality they offer are clear. However, their integration into vehicles alongside other beam projection systems remains largely unexplored and presents significant space constraints.

[0048] There figure 2 presents an example of an embodiment of the present invention which allows for a relative placement of the light source and the improved optical input device relative to the prior art.

[0049] From upstream to downstream, following the path of the light rays, a light source 21 is present, which may be of the type previously described. Preferably, the light source 21 is configured to emit in a hemisphere from a rectangular emitting area. At least a portion of the rays emitted by the source 21 is optically processed by an optical device 22. This device may comprise one or more lenses of more or less complex shapes.

[0050] To the figure 2 The optical device 22 takes the form of a lens having an entrance face 22a for admitting light rays from the source 21 and an exit face 22b for projection towards the rest of the module. At the output of the optical device 17, at least a portion referred to as "a", called the transmitted portion of the processed rays, is intended to impact the surface of the pixelated and digital imaging system, here a micromirror array 23. However, according to the invention, the light rays first enter through a prism 26, via a first face 26a thereof.

[0051] Preferably, the first face 26a forms an acute angle with the average direction of the transmitted portion "a" of the light rays coming from the source 21. More preferably, the average direction and the normal to the first face 26a form an angle between -20° and +20°. Preferably, the angle formed between the first face 26a and the third face 26c is between 40° and 50°.

[0052] In general, it is desirable to use for prism 26 a transparent material which advantageously has a high Abbe number, preferably greater than or equal to 50. According to the invention, this is Crown glass or polymethyl methacrylate (PMMA).

[0053] The light rays entering prism 26, referenced as "a" in figure 2 The light rays are directed towards a third face 26c of the prism 26, opposite which the imaging system is located. In the example shown, this system is a micromirror array 23. Advantageously, the impact surface 24 (corresponding to the exposed surface of the micromirrors) is parallel to the third face 26c, the latter preferably being flat. The impact surface 24 is protected by a glass pane 27, a first face 27a of which is located opposite the impact surface 24. A second face 27b of the glass pane 27 is located opposite the third face 26c. The second face 27b and the third face 26c are spaced apart so that a space exists between them, a space which is filled by the interface 30 so that there is no residual air space between the interface 30 and the faces 26c, 27, on the path of the light rays.

[0054] Advantageously, the distance between the impact surface 24 and the third face 26c is limited and can, for example, be less than 2 mm or even 1 mm, and preferably 0.5 mm. The presence of the glass 27 can be used to adjust this gap without risk of damaging the impact surface 24.

[0055] Thus, the glass 27 and the prism 26 are joined via an interface 30. This interface can also serve as a point of adjustment for the overall thickness of the light transmission exiting the prism onto the impact surface 24. More precisely, the interface 30 is located at the contact between the second face 27b of the glass 27 and the third face 26c of the prism 26. Advantageously, the third face 26c and the second face 27b are parallel, so the thickness of the interface 30 is continuous. Here, "thickness" refers to the dimension of the interface 30 directed perpendicularly to the faces in question.

[0056] One aspect of interface 30 is to completely fill the space between the prism and the glass with a solid medium. For this purpose, contact of interface 30 on each of faces 26c and 27b is sufficient, even without adhesion to these faces. However, the interface can also provide a mechanical bonding effect, forming a coherent assembly with at least one of the prism and the glass.

[0057] Preferably, the interface 30 is achieved using a single layer of a transparent material, in particular an optical adhesive. In terms of the process, a liquid adhesive film, the precursor of the interface, can be deposited on one of the second face 27b and the third face 26c, then the other of these faces can be applied to the deposited film, and the adhesive can be cross-linked. An adhesive cured under ultraviolet light can be used, for example. The adhesive can be sensitive to ultraviolet light in a wavelength range between 320 and 380 nanometers. Cross-linking by annealing is also possible.

[0058] It should be noted that interface 30 forms a solid portion. By solid, we mean a state of matter that is neither gaseous nor liquid, which does not exclude the possibility that interface 30 is made of a soft material, for example an elastomer or in the form of a paste.

[0059] The interface 30 creates a solid continuity between the prism 26 and the glass 27. To make this continuity as optically efficient as possible, it is advantageous for the refractive index of the interface 30 to be identical or similar to the refractive index of at least one of the materials of the glass 27 and the prism 26. For example, a prism and glass made of Crown glass, particularly with a refractive index of 1.52, can be used, or a prism made of polymethyl methacrylate (PMMA) with a refractive index of 1.49 and a glass pane 27 (particularly Crown glass with a refractive index of 1.52). The material of the adhesive interface 30 is then chosen to be identical or similar to these refractive indices. For example, the optical adhesive marketed by Norland Products Inc. under the reference "Norland Optical Adhesive 83H" can provide a satisfactory solution, with a refractive index of 1.56.The term "similar" refers to optical indices that differ by no more than 10% in magnitude and / or are not more than 0.15 in refractive index value. Preferably, the refractive indices of the prism, the glass, and the interface are all within a range of 0.15 in refractive index value and / or 10%. However, a wider range is acceptable, particularly when the refractive index of the interface is intermediate between the refractive indices of the prism and the glass (this is generally preferred if the refractive indices are different). In this case, the refractive indices of the glass and the prism can be such that each is no more than 10% and / or 0.15 from the refractive index of the interface.

[0060] In the illustrated embodiment, the aim is also to eliminate, or at least limit, the unwanted effects that could result from reflections of rays reaching the impact surface 24 and being reflected onto the first face 27a of the glass. To this end, the glass 27 is fitted with an anti-reflective coating 28, which may be of a standard design and, in particular, configured to produce a maximum reflection of 4%, or even a maximum of 2%, in the visible spectrum. Preferably, the anti-reflective coating is chosen with a maximum reflection of 1% in the visible spectrum.

[0061] Preferably, the impact surface 24 defined by the set of micro-mirrors is rectangular in shape. It preferably extends in a plane perpendicular to a plane carrying the second face 26b of the prism 26 and / or parallel to the optical axis of the projection device 25.

[0062] Depending on the orientation of the mirrors, the rays are reflected either in such a way as to contribute to the projected beam or to remain inactive. This allows the configuration of the pixelated beam to be controlled at will. In the case shown, the active rays "c" are directed to re-enter prism 26 through the third face 26c. This ray path is configured so that the active rays "c" again reach the first face 26a. However, this time, the angle of the rays relative to the first face 26a is such that total internal reflection occurs within prism 26, forming reflected rays "d" which are directed towards the second face 26b of prism 26.

[0063] The outgoing rays "e" are directed towards a projection device 25, which is or typically includes a projection lens. In the illustrated case, this is a plano-convex lens, whose entrance face 25a is flat and whose exit face 25b is convex. The reference "f" represents an example of a projected ray.

[0064] Advantageously, the prism 26 is configured, in terms of angle and choice of materials, so that all the light rays from the input device 22 are transmitted to the micromirror array 23 and so that all the light rays reflected by the latter are reflected by the first face 26a. It should be noted that the area of ​​the first face 26a through which the rays "a" enter the prism 26 and the area of ​​the first face 26a through which the rays "c" reach the first face 26a again to be reflected, may overlap.

[0065] The invention is not limited to the embodiments described but extends to any embodiment covered by the claims. REFERENCES

[0066] 11. Light source 12. Optical device 13. Micromirror array 14. Reflecting surface 15. Projecting optical device 21. Light source 22. Input optical device 22a. Input face 22b. Output face 23. Micromirror array 24. Impact surface 25. Projecting optical device 25a. Input face 25b. Output face 26. Prism 26a. First face 26b. Second face 26c. Third face 27. Glass 27a. First face 27b. Second face 28. Anti-reflective coating 29. Optical axis 30. Interface

Claims

1. Lighting module for motor vehicles configured to produce an output beam, comprising a light source (21) comprising at least one light-emitting diode, a pixelized and digital imaging system, and an input optical device (22) on the path of the light rays from the light source (21) between the light source (21) and the pixelized and digital imaging system so as to transmit at least a part, termed the transmitted part, of the light trays from the light source (21) toward an impact surface (24) of the pixelized and digital imaging system, including: - a prism (26), comprising a first face (26a), a second face (26b) and a third face (26c) and configured: ∘ to transmit between the first face (26a) and the third face (26c) at least a part of the light rays from the part transmitted toward the impact surface (24); ∘ to form reflected rays by reflection of at least a part of light rays redirected by the impact surface (24) by total internal reflection at the first face (26a); ∘ to redirect at least a part of the reflected rays toward a projection zone via the second face (26b); characterized in that it comprises a window (27) disposed between the impact surface (24) and the third face (26c) and a solid interface (30) joining the third face (26c) and a face (27b) of the window (27) disposed facing the third face (26c); the material of the interface (30), that of the window (27) and that of the prism (26) having a same optical index or optical indices not differing form one another by more than 10%. the prism (26) being in PMMA or Crown glass, and another face (27a) of the window situated in front of the impact surface (24) comprising an antireflection coating (28).

2. Module according to the preceding claim, in which the interface (30) is a polymerized optical adhesive.

3. Module according to either one of the preceding claims, in which the maximum thickness of the interface is less than 1 mm, or even 0.5 mm.

4. Module according to any one of the preceding claims, in which the third face (26c) and the face (27b) of the window (27) are parallel.

5. Module according to any one of the preceding claims, in which the second face (26b) and the third face (26c) are carried by two mutually perpendicular planes.

6. Module according to any one of the preceding claims, further including an optical device (15) for projecting the output beam receiving at least partly the at least a part of the redirected rays.

7. Module according to the preceding claim, in which the optical projection device (15) has an optical axis (29) perpendicular to the second face (26b).

8. Module according to either one of the previous two claims, in which the optical projection device (15) has an optical axis (29) forming an obtuse angle with a mean direction of the transmitted part.

9. Module according to any one of the preceding claims, in which the mean direction of the transmitted part forms with a normal to the first face an angle between -20° and +20° inclusive.

10. Module according to any one of the preceding claims, in which the pixelized and digital imaging system comprises a micromirror matrix (23).

11. Module according to any one of the preceding claims, in which the output beam is configured to project at least one pictogram pattern.

12. Module according to any one of the preceding claims, configured to project a light beam in front of a motor vehicle.

13. Motor vehicle lighting and / or signalling device equipped with at least one module according to any one of the preceding claims.